Reinforced brake lining and method of making same



Jllly 22, 1952 c. s. BATcHELoR ET AL 2,604,425

REINFORCED BRAKE LINING AND METHOD OF MAKING SAME Filed Nov. 29, 194e Mor/leylalented` `uly 22, 195i acm-nso PAT oFF-rcs* IREINF()RCE'DEBR-AK LINING N D MTHO '0F MAKING SAME YUlydeS.Batchelor,Henry J .'eCo'fek, anlFredeick V""S. "Walker, Bridgeport, Conny, assigfn'orsto Ray- V`bestes-Lllilanh-attan, :,Inc., flassaic, ',N. al., a toorrporationfof New Jersey Application November 29, 1946, VSerial No. '712818 This inventionrelates `to"iImprovementsin brakeliningsl 'of tnesegmjental type anda"methodfoi making :the same, Jand refers particularly to a brake lining of fthe molded or'eXtliudd'-WDB-.having 'a `'heat h'ardenabl'e jbinder and ar'reinforced back.

Infth'e mamifacture Aofb'iake linings of the class described it has been found that tl1e^usual frictin materi'al'having `a"heat harclenable 'binder shrinks, tha/tis, permanently'red-uces dimensions during the period when it iis "sribjectedjto 'ternperaitres necessary to harden the material In addition, -i-t is'frequ'ently necessary ito,rein-Torce such linings, :and this has-fl1ereto`fore been accomplished by embedding-"a-fmetallicinesh in the rear -orconcave face oftle lining. l Y

In hardening -or fcringsai'd linings the same are s-uloj'ected to -levatedlteiriperatur'e'sfor a lpredetermined 'perio'd 1 of time 'found necessary '5to drive off volatiles, 'oxidize-binders .land 'accomplish the necessary 'cozmzilex reactions `wlfiicli Sgo 'to hard-en "the friction material.

- In View 'of fthe inherent l'o'harial:ter-istics v'ijf fsuh materials to shrink --fat the 'hardening temperatures employediland ltnefte'ndencyof the metallic reinforcing strands' ito expand l"at the "same time,

it :has '.been ffoundztnat the 4'segmeni-s warp, fthe interna-1 :stresses-exhibiting 'thems'elves by a "strain or deformation characterized in that the segment buckles transversely with; the unreinorc'ed for workingside :concave fand 'the reinforced or iinner ,iside i'convex. 'This condition necessitates excessive :grinding of the face-tof Vthe segment which, of course, is awasteful and laborious fprocess.

'Ascmewha-t similar Vvcondition :also fexi'sts'during :usage :or loperation'of kthe bra-ke lining, iparticularly Where th'elfliningh'as motbeen :completely fc'ured. During severezusagewhere-heat iat high temperature ;is generated, additionalrshrinkage of the lining vsometimes takes ,plaeefwaugmented by :the -expansionrof thetransverse 4reinforcing strands. Consequently, transverse vWarpa'g'e iis likelytooccur, :resulting -i-n..highA spots or hard spotson the .lining and ,maldistri'bntion of .frictional lforces. y

, yAs a yfeature .ofour .invention :we incorporate a rinorcingmaterial, preferably a ineshmaterial having non-metano 'transverse strands eenstrctdfofa material which 'also shrinks at 'the ynardeing ori-curing 'temperature of the friction material. "Byt'he incorporation' of Lsuch 'material theshrinkageo tnefric'tji'cn'material perse is compensatedffor by the shrinkage'oi the trzmsverse reinforcing strands and VKthe stresses are,

hence, balanced or overbalanced, if desired, and

foreingnres'hein eddedtherei-n V ing Y-nonmetallic transverse strands ingni'aterial lwhich naves'lrrinlageclarac at hardenin'gorcr'ing ltexmzni-tnres.

Fig. -4 is a" fragmentary l "ew Aof a mesh'reinforc i'ng k'materia-l"constructed in Irvacco'rdanc'e'v'sitli '-)tl'e concepts of our invention. Y

Figf vis ran enlarged View of onelfor'rn :of A'none neta-llic vcross'stra''1r 'i"`f 'n-m:d suitable 'in our invenion. Referring in detail to the drawing, I indicates a ksegr'nental -brake lining 'whichis constrctd of a vfriction material `vhaving fa yneat vfhar lle binder. Ourfinventionhasf'specifrcapih at' itc theniolded--or extrnfled-typeio'f'brak lining general "to those-types 'f ning 'which Afre'ly--fr strengtlr-up'en-fafheat ha-rdenable "ty-pe lof 'friction material is jbest=5-exen11i= lied 'by "the asbestos-fill binder `yp'e i the binder being lgenerally lconiposed'l dri/"rigl oil, a more Ior `lessV smal-1 'amount icfriib'b an *a solvent. is'a-tyicalfe" 'ic' ing lis l'subjectedto "heat-.fata'ftemperatnreior th oraemecessaryfmhard degree ofitemperature manufacture 'of ftloefbrat i e norcure -tnebi ris For purposes of further example, the abov e'-v scribed irri(:tionrfu 1arterial,iis trateror a manner simfilar'to'lthat eescriben 1i-n the eend'-l ingapplieation for iUnited :States letterat ft- 5e8,e23,'now iab'andfo dit@ preemcefaloose mass of smaiiipelietser unes cf-fnsrea'somtiies characterized avs'lbelngnf Ta granular nf'atre 'l owed by gravity! between fa .pair df'frellsfwiil compact and shape the mass and continuously discharge the same in the form of a strip of ma-A terial of a densied nature. The composition of the class hereinbefore described, particularly when the rubber content thereof is low, requires reinforcement and support, especially during the initial handling stages and subsequent curing or hardening stages and for this purpose, as the compacted material is extruded between the rolls, there is simultaneously embedded in one face thereof a Woven mesh reinforcement. 1

Such reinforcements, heretofore haveV usually comprised a woven wire mesh having wire for both the warp and weft strands, as Yshown particularly in Fig. 2, wherein 2A indicates a portion of a segmental brake lining composed of a friction material 3 and woven longitudinal strands Y 4 and cross strands 5 of wire.

When the element 2 is heated to cure or harden the binder, the friction material tends to shrink.

Simultaneously, the cross strands 5 tend to expand, vsetting up internal stresses `in the element which result in the same being .dished transversely, that is, the Working face becomes trans- -versely concave and the rear face, or longitudinally concave face of the segment becomes transversely convex. This, of course, requires that the working face be ground, or if not ground, high spots or hard spots develop during usage. y

In accordance with our invention a reinforcement 6 is embedded in the rear or concave face of a segmental brake lining 1, the reinforcement comprising a woven structure including longitudinal metal strands 8 and transverse non-metallic strands S. The strands 9 are so constructed or comprise a material whichwhen heated to temperatures in the neighborhood of the hardening temperature ofV the friction material will shrink, that is, exert a tensile force which opposes the shrinkage of the friction material per se.

YWhen the friction element 1 is subjected to hardening temperature, `the stress due to the shrinkage of the friction material per se, is resisted by the stress due to the shrinkage of the strands V9 and as a consequence the element 1 is prevented from buckling concave transversely,

as'was the case with the element 2. It is con-4 templated that the strands be of suicientnumber, cross-sectional areaA and possess suicient latent shrinkage properties as to balance the shrinkage stress ofthe friction material per se, orthat the strand shrinkage stress be slightly greater than the shrinkage stress produced by the friction material, in which case the element 'I maybe buckled slightly convex transversely.l This latter condition is not particularly troublesome in the use of segmental brake linings.

As an example of the type of material comprising the cross strands 9, nylon may be used either as monolaments or yarn. Nylon possesses the property of contracting when subjected to temperatures in the hardening temperature range of the friction material, the maior portion of the hardening or curing taking place between about 200,and 300 F., Within which range nylon also shrinks. Y 1 Y,

Another material which can be employed for the strandsQ comprises twisted paper, particularlyv kraft paper, as shown best at I0 in Fig. 5. It is believed that the twisting, which imparts tension to the paper, augments the normal tendency of a paper cord or strand to contract when the same is heated. At least, such a `material when used as therme- Strands eliminates the.

4 condition illustrated in Fig. 2, when the segment is cured or hardened.

To'use the twisted paper strands I0, it is preferred that a mesh structure be formed comprising wire Warp strands and twisted paper filler strands, as illustrated in Fig. 4. To facilitate the handling of the mesh or screen so formed, the same, after Weaving, is coated with an alkyd resin or other type'resin as described in the patent to D. H. Miller et al., No. 2,403,674.

i InV view of the fact thatthe resin coating is baked after application of said coating to the mesh, a degree of latent shrinkage of the transverse strands may be lost. However, in the manufacture of brake linings, if the baking temperature of the resin on the mesh is maintained not materially above 200 F., sufcient latent shrinkage of the cross-strands will be retained to resist or overpower the inherent shrinkage of the friction material per se during hardening or cure. It is essential that the cross-strands during hardening or cure be capable of shrinking at least one-half percent of their length. Preferably, the shrinkage should be of the order of about two and one-half percent, although shrinkage as high as ten percent may not be excessive, particularly in those uses where overbalance of the stresses is desired in Yfavor of the strands.

In addition to having characteristics of shrink-,- age at hardening or curingvtemperatures, the transverse strands, particularly Where used as a prefabricated mesh should have suiicient strength and stiffness to be woven, and iffthe material is extruded, to go through the extrusion step Without distortion. Y

In operation, brake linings are frequently heated to relatively high temperatures, depending upon the severity of the'use. When reinforced segmental linings are employed having metallic cross-strands aswell as metallic longitudinal strands, such heating `tends to buckle the lining transversely, due in some instances to an incompletely cured lining and. by the presence of the expandibleY metal cross-strands. The latter-.is frequently the predominating cause of such buckling even when the lining itself is cornpletely cured, and the buckling is always such as to have the working face warped transversely concave.

In employing our invention such transverse buckling of the Working face to a Vconcave contour is v not only prevented during hardening or cure but is also prevented during use.V Although it is possible that in curing or hardening the latentshrinkage of the transverse strands, may, in some instances be exhausted after such cure or hardening'said strands, unlike metal strands, when in use, do not actively warp the lining and to this extent function in a superior manner to the metallic transverse strands. However, where, in some instances, latent shrinkage is retained in the transverse strands even after c urej or hardening, such strands function in operation in a manner as hereinbefore described during our# ing or hardening. y Y

Of course, it is to be understood that our invention is not intended to be limited to a friction material containing only the specific 'in--V 'We 'claim asour invention: Y e f 'll'.:Afmethod of making a heat hardened 'reinfomed 'brake lining of the arcuate-segmental type having a longitudinal vconvex and concave faceand :constructed of a friction materiali-raving -a v"lieathardenable binder ywhich shrinks yat hardening temperatures comprising, embedding a reinforcing material Ain said segment `comprising longitudinal `portions and pertionsdisposedtransversel-y to fthe-arc 'of Jthe segmentand adj acent-the concave vface thereof, said ytransversely disposed portions consisting-of strands having char-acteristicsof producing-shrinkage stresses transversely of the segment-adjacent-the concave face thereof at Lthe hardening temperatures `of the binder, and hardeningsaid friction material at elevated tempera-tures 'with said reinforcing material in situ. 12.-A-'-r'nethod of makinga heat hardened L,reinforced brake lining of the arcuate segmental type having a longitudinal convex and concave face and 4constructed ofa friction material having a'heat hardenable binder which shrinks at hardeningtemperatu'recomprising, embedding a reinforcing material in said segment consisting of spaced strands transverse to the `arc of the segment and adjacent the concave facethereof, said spaced lstrands of reinforcing material having characteristics of producing shrinkage stresses transversely of the segment Aadjacent the concave face thereof which atleast balances the shrinking'stresxses'producedv by the shrinking of the heat hardenablebinder at the hardening temperatures of the-binder, and hardening said friction material at elevated temperatures with said reinforcing material in situ.

3. A method of making a heat hardened reinforced brake lining of the arcuate segmental type having a longitudinal convex and concave face and constructed of a friction material having a heat hardenable binder which shrinks at hardening temperatures compr-isingembedding a reinforcing material in said segment adjacent the concave face thereof comprising spaced strands disposed longitudinally and transversely Ito lthe arcof the segment, said 'transversely disposed spaced lstrands of reinforcing material having characteristics of producing shrinkage stresses transversely of the segment adjacent the concave face thereof at the hardening temperatures of the binder, at least equal to the stress produced by the shrinkage of the binder, and hardening said friction material at elevated temperatures with said reinforcing material in situ.

4. A method of making a heat hardened reinforced brake lining of the arcuate segmental type having a longitudinal convex and concave face and constructed of a friction material having a heat hardenable binder and which produces shrinkage stressesv at hardening temperatures comprising, embedding a reinforcing material in said segment comprising spaced longitudinal strands and spaced strands transverse tothe arc of the segment and adjacent the concave face thereof, said spaced transverse strands consisting of reinforcing material being so disposed and having characteristics of shrinking at the hardening temperatures of the binder such as to produce counter shrinkage stresses, greater than those of the friction material, and hardening said friction material at elevated temperatures with said reinforcing material in situ.

5. A method of making a heat hardened reinforced brake lining of the arcuate segmental type having a longitudinal convex and concave face and constructed of a friction material having a heat -hardexiable binderfwhich "shrinks and produces shrinkage stresses at 'hardening temperatures comprisingembedding -a mesh reinforcing material in said segment consisting of portions disposed llongitudinally andl transversely lto Athe arc of i the-segmentand adjacent the-concave face thereof, said-transversely disposed portions being so -conditioned and having -characteristics lof lshrink-ing at-the hardening temperatures ofthe binder `such as to produce shrinkage lstresses counterfto those ofv theybinder, and hardening said friction-material at elevated ytemperatures with said reinforcing material 'in situ.

6. A method of making a heat hardened reinforced brake lining of the arcuate segmental type having a longitudinal convex and concave vface and constructed of a friction material having a heat -hardenable 'binder which shrinks andr produces transverse `tension at hardening temperatures consisting of embedding a reinforcing material in said lsegment having metallic portions extending longitudinal of the arc of the segment and non-metallic portions extending transversely to the arc of the segmentadjacent the concave face thereof, said transversely disposed portions being so positioned and having characteristics of shrinking at the hardening temperatures of the binder'such as to produce tension stresses counter to the binder Ytension stresses, and hardening said friction material at elevated temperatures with said reinforcing material in situ.'

'7. A method of 'making a heat hardened reinforced brake lining of the arcuate -segmental type having a longitudinal convex and concave `face and constructed of a friction material having a heat hardenable binder and which shrinks and produces shrinkage stresses transversely of the lining at hardening temperatures comprising, embedding a mesh reinforcing material in said segment consisting of metallic strands extending substantially longitudinally of the arc of the segment and non-metallic cross strands extending transversely to said arc adjacent the concave face thereof, said cross strands being so disposed and having characteristics of shrinking at the hardening temperatures of the binder such as to Aproduce transverse shrinkage stresses adjacent the concave face of the brake lining, and hardening said friction material at elevated temperatures with said reinforcing material in situ.

8. A method of making a heat hardened reinforced brake lining of the arcuate segmental type having a longitudinal convex and concave face and constructed of a friction material having a heat hardenable binder and which shrinks and produces transverse shrinkage stresses upon the lining athardening temperatures which comprises embedding a reinforcing material in said segment consisting of metallic longitudinal strands and strands of organic fibrous material disposed transversely to the arc of said Asegment andadjacent the concave face thereof said strands of organic fibrous material being so initially conditioned as to produce transverse shrinkage stresses adjacent the concave face of the lining when the binder is subjected to hardening temperatures, and hardening said friction material at elevated temperatures with the organic brous strands in situ.

9. A method of making a heat hardened reinforced brake lining of the arcuate segmental type having a longitudinal convex and concave face and constructed of a friction material having a heat hardenable binder and which shrinks and produces shrinkage stresses transversely of the lining at hardening temperatures which comprises, embedding a reinforcing material in said segment consisting of Y longitudinal metallic strands and strands of paper disposed transversely tothe arc of the segment and adjacent the concave face thereof, said paper strandsvbeing initially so disposed in 4said lining and havingV characteristicsY vof shrinking at the hardening temperature of the binder such as to produce counter, transverse shrinkage stresses adjacent the concave face ofthe lining and hardening said friction material at elevated temperatures with the paper strands in situ. Y

l0. A method of making a heat hardened reinforced brake' lining of the arcuate segmental type having a longitudinalconvex and concave face and constructed of afriction material having a heat hardenable binder which shrinks and produces shrinkage stresses transversely ofthe lin- Y ing at hardening temperatures Which comprises,

embedding a reinforcing material in said segmentV adjacent the concave face thereof consisting of longitudinal metallic strands and strands of nylon disposed transversely to the arc of the segment, said nylon strands being initially sol disposed and having characteristics of shrinking at the hardening temperature of the binder such as to produce counter transverse shrinkage stresses adjacent the concave face of the lining, and hardening said friction material at elevated temperatures with the nylon strands in situ.

11. An intermediate product in the manufacture of an arcuate segmental brake lining having a longitudinal convexA and concave face which comprises heat hardenable friction material which shrinks at hardening temperatures having embedded in the concave face thereof a .mesh reinforcing material consisting of continuous longitudinal portions and portions extending transversely to the arc of said segment, said "transversely extending .portions having characteristics of shrinkage at the hardening temperatures of the frictionv material, and being so initially tensioned as to produce shrinkagestresses 'upon the lining when the binder is hardened.V

12. An intermediate product in the manufacture of an arcuate segmental brake lininghaving a longitudinal convex and concave face which comprises heat hardenable friction material which shrinks at hardening temperatures having em bedded in the concave face thereof a mesh reinforcing material consisting of metallic members extending substantially longitudinally and sub- Stantially continuous non-metallic portions extending transversely to the segment, said transversely extendingl portions having characteristics of shrinkage at the hardening temperatures of the friction material, and being so initially tensioned as to produce shrinkage stresses upon the lining when the binder ishardened.

13. An intermediate product in the manufacture of an arcuate segmental brake lining having a longitudinal convex and concave face which comprises heat hardenable friction material which shrinks at hardening temperatures having embeddedjin the concave face thereofa mesh reinforcing material consisting of metallic members extending substantially longitudinally and nonmetallic portions extending transversely to and across substantially the entire transverse Width ofv the segment, saidv transversely extending portions comprising paper strands having characteristics of shrinkage atthe hardeningtemperatures of the friction material, and being so initially tensioned as to produce shrinkage stresses upon the lining When the binder is hardened.

Y CLYDE S. BATCHELOR.

HENRY J. COFEK. n FREDERICK S. WALKER.

REFERENCES CITED The following references are of'record in the iile of this patent:

` UNITED STATES PATENTS Number 

1. A METHOD OF MAKING A HEAT HARDENED REINFORCED BRAKE LINING OF THE ARCUATE SEGMENTAL TYPE HAVING A LONGITUDINAL CONVEX AND CONCAVE FACE AND CONSTRUCTED OF A FRICTION MATERIAL HAVING A HEAT HARDENABLE BINDER WHICH SHRINKS AT HARDENING TEMPERATURES COMPRISING, EMBEDDING A REINFORCING MATERIAL IN SAID SEGMENT COMPRISING LONGITUDINAL PORTIONS AND PORTIONS DISPOSED TRANSVERSELY TO THE ARC OF THE SEGMENT AND ADJACENT THE CONCAVE FACE THEREOF, SAID TRANSVERSELY DISPOSED PORTIONS CONSISTING OF STRANDS HAVING CHARACTERISTICS OF PRODUCING SHRINKAGE STRESSES TRANSVERSELY OF THE SEGMENT ADJACENT THE CONCAVE FACE THEREOF AT THE HARDENING TEMPERATURES OF THE BINDER, AND HARDENING SAID FRICTION MATERIAL AT ELEVATED TEMPERATURES WITH SAID REINFORCING MATERIAL IN SITU.
 11. AN INTERMEDIATE PRODUCT IN THE MANUFACTURE OF AN ARCUATE SEGMENTAL BRAKE LINING HAVING A LONGITUDINAL CONVEX AND CONCAVE FACE WHICH COMPRISES HEAT HARDENABLE FRACTION MATERIAL WHICH SHRINKS AT HARDENING TEMPERATURES HAVING EMBEDDED IN THE CONCAVE FACE THEREOF A MESH REINFORCING MATERIAL CONSISTING OF CONTINUOUS LONGITUDINAL PORTIONS AND PORTIONS EXTENDING TRANSVERSELY TO THE ARC OF SAID SEGMENT, SAID TRANSVERSELY EXTENDING PORTIONS HAVING CHARACTERISTICS OF SHRINKAGE AT THE HARDENING TEMPERATURES OF THE FRICTION MATERIAL, AND BEING SO INITIALLY TENSIONED AS TO PRODUCE SHRINKAGE STRESSES UPON THE LINING WHEN THE BINDER IS HARDENED. 